Name

PostGIS_DropBBox — Drop the bounding box cache from the geometry.

Synopsis

geometry PostGIS_DropBBox(geometry geomA);

Description

Drop the bounding box cache from the geometry. This reduces
geometry size, but makes bounding-box based queries slower. It is also used to drop a corrupt bounding box. A tale-tell sign of a corrupt cached bounding box
is when your ST_Intersects and other relation queries leave out geometries that rightfully should return true.

Bounding boxes are automatically added to geometries and improve speed of queries so in general this is not needed
unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes.
Then you need to drop the old and readd. This kind of corruption has been observed in 8.3-8.3.6 series whereby cached bboxes were not always recalculated when a geometry changed and upgrading to a newer version without a dump reload will not
correct already corrupted boxes. So one can manually correct using below and readd the bbox or do a dump reload.

This method supports Circular Strings and Curves

Examples

--This example drops bounding boxes where the cached box is not correct
--The force to ST_AsBinary before applying Box2D forces a recalculation of the box, and Box2D applied to the table geometry always
-- returns the cached bounding box.
UPDATE sometable
SET the_geom = PostGIS_DropBBox(the_geom)
WHERE Not (Box2D(ST_AsBinary(the_geom)) = Box2D(the_geom));
UPDATE sometable
SET the_geom = PostGIS_AddBBox(the_geom)
WHERE Not PostGIS_HasBBOX(the_geom);